Cool concept and demo, I also think the combination of Metroidvania with bullet hell has a lot of potential! I liked the enemy variety and the bullet patterns, and the boss was also very fun and decently challenging.
However, in my opinion the rocky background kinda clashed with the overall "space shooter" vibe, I think a starry sky background with asteroids, debris, or some sort of space station scaffolding as "walls" might have worked better there.
I'm also not sure which one of the mandatory themes you went with (Unity, Unreal, Construct, Rust, Python, Pearl). I guess Construct is probably the closest since most enemies look like robotic turrets?
Regardless, I had a lot of fun with the game, good job!